Selector bank for automatic telephone systems



p 1950 H. HARVEY 2,523,622

SELECTOR BANK FOR AUTOMATIC TELEPHONE SYSTEMS Filed Feb. 20, 1948 Patented Sept. 2 6,- 1950 UNITED STATES PATENT OFFICE SELECTOR BANK FOR AUTOMATIC TELEPHONE .sYsTEMs Application February 20, 1948, Serial No. 9,743 In Australia February 24, 1947 5 Claims. 1

This invention relates to selector banks, either of the bimotional type or of the uniselector type, which are intended to be mounted in sets in the shelves of automatic telephone equipment.

Construction of selector banks of the bimotional type as now adopted in modern equipment, is carried out in two operations. It is usual in the first operation to apply a plurality of contacts radially to an arcuate strip of adhesive insulating cloth, the reverse side of which is applied to an arcuate strip of insulating board. These arcuate strips with the contacts adhering thereto are then, in the second operation, assembled with arcuate insulating separators between them to form levels each of which is separated from its adjoining level by a screening plate usually of aluminium.

Usually there are ten levels in each bank of the bimotional type, and as the construction at present adopted involves several layers of components in each level, the total number of layers in each bank, including the aforesaid screening plates, in seventy-nine.

For eificient service it is essential that these banks when assembled should conform fairly rigidly to stipulated dimensions and, in practice, any departure from prescribed tolerances results in banks being rejected by authorities responsible for installation of telephone equipment.

It will be appreciated that with the multiplicity of layers now adopted, any slight variation in the thickness of the respective layers can have an accumulative effect which would place the bank beyond the prescribed tolerance.

The present'invention has been devised primarily with the object of facilitating assembly of the selector banks and simplifying their construction.

The invention results in substantial reduction in the number of layers involved in construction of the banks, with consequent material reduction in the extent of departure from stipulated di mensions. I

According to the present invention the contacts as ordinarily employed are assembled in radially disposed grooves formed in an arcuate separator of moulded plastic material having good insulating properties and high dimensional stability. Polystyrene isone appropriate ,-ma-.

terial for this purpose. The grooves arev accurately formed in the process of' moulding, and serve to hold the contacts in their correct location while the bank is being assembled. The grooves are of such depth that the outer faces of the contacts lie substantially flush with the surface of the plastic separator. The faces of such contacts may, however, protrude sufficiently to ensure rigid clamping of the contacts when the several plastic separators, with intervening insulating separators and screen segments hereinafter referred to, are assembled and secured together to constitute the bank.

In order however, that the invention may be fully understood and readily carried into practical effect, reference is now made to the drawings accompanying and forming part of this complete specification.

Figure 1 is a plan of a bimotional selector bank embodying the present invention;

Figure 2 is a plan of one of the aforesaid plastic separators as utilized in the bank illustrated by Figure 1;

Figure 3 illustrates section of the plastic separator as indicated by the line 33 in Figure 2, on an enlarged scale;

Figure 4 is an expanded sectional view indicating, schematically, portion of a selector bank embodying the present invention; and

in Figure 2) is quite plain, whilst the other face has accurately formed in it a plurality of grooves I2 to receive contacts I3. These contacts fit closely within the grooves I2, and as will be observed on reference to Figure 4, the contacts I3 lie substantially flush with the face of the separator in which they are set. In of each level with contacts I3 so arranged in them are disposed face to face as indicated in Figure 4, with the intervening insulating separator II between them. It will be noted that each of the grooves l2 in the separators I0 has an angularly disposed portion I4, so that when the several separators are assembled the terminal portions of the contacts I3 projecting beyond one of the separators II] will project at an angle in relation to those projecting from the other separator l0 of the same level, as will be apparent on reference to Figure 1.

The two separators The insulating separators l I may be of phenol fibre or any other appropriate insulating material, but preferably they are of a paper base.

Between each of the levels L there is a relatively thin screening segment 15 which preferably is of copper foil. These segments l have integral tags such as I 6 (see Figure 5) which are; arranged to project alternatively at each end. of the bank and are folded in to make electrical contact with the relative end of the next succeeding segment I5 in accordance with existing, practice.

Ten of the levels L together with screening segments l5 are assembled as explained; and these are clamped between upper and lower plates 11, preferably of steel, the whole being secured together as by screws l8 (Figure 1).

The foregoing construction and arrangement of the several components materially reduces the total number of layers in the bank. Moreover the great reduction in the total number of components adopted, materially reduces time absorbed in assembling the bank and in the subsequent maintenance thereof; and it will be appreciated that with the smaller number of components, the cumulative effect of incidental departures from prescribed measurements of the individual components will be considerably less than in banks constructed in accordance with existing practice. In some instances the contacts l3 may be set in the separators I0 during the process of moulding.

Whilst the invention has been described more particularly with regard to banks of the bimotional type, it will be understood that the mode of-construction may be applied with equally satisfactory results to banks of the uni-selector p I claim:

1. A selector bank, for use in automatic telephone equipment comprising a pluralityof levels! each of which consists in-a pair of arcuateinsulating plastic separators, an intervening insulating separator, and aplurality ofcontacts rigidly. held between said plastic; separatorsv and said insulating separator, the opposed'faces of said arcuate plastic separators having shallow.

accuratelydefined grooves therein, and said .contacts being accommodated in said grooves. and lyingsubstantially flush with the innerfaces of the arcuate plastic separators.

2.; Aselector bank, for usein automatic tele phone equipment, comprising a; plurality of levels each of which consists in a pair of arcuate insulating plastic separators, an intervening insulating; separator, and a plurality of contacts,

the opposed faces of said arcuate plastic separators having accurately defined shallow. grooves therein and said contacts being rigidly held 3. A selector contact bank for use in automatic telephone equipment comprising aplurality-of superimposed contact levels each consisting in a pair of insulating plates of arcuate plan and uniform thickness, an insulating plate between and separating said arcuate plates, said intervening platebeing arcuate inplan and having a radial extent greater than said; first mentioned plates, the opposed faces of said arcuate plates having accurately defined substantially radially extendinggrooves provided therein, each groove having a planar base surface and the portion of the face of each plate between the respective grooves therein being a planar surface, and a plurality of' similarly formed contacts having opposite planar surfaces and a thickness substantially equal to the depth of said grooves and disposed in said grooves with one planar face contacting theplanar base surface of the grooves andtheopposite outer planar face of each contact being disposed substantially flush with the adjacent planar base portions of the said arcuate plates.

4; A selector contact bank: comprising a plurality of' superimposed contact levels each consisting in a pair of'similarly' formed insulating plates arcuate in plan and having uniform thickness, an insulating plate between and separating the said arcuate plates, each of said arcuate plateshaving a plurality of spaced, radially ex tending grooves accurately defined therein, each groove having a planar basesurface and including an angular extending portion adjacent the longer perimetrical edge of said plate, a plurality of similarly formed contact members of uniform thickness substantially the same as the depth of said grooves andeach havingan angularly ex-- tending terminal portion, the plates-being disposed in opposed relation with the grooved sides thereof facing one another on opposite sides of said separator plate and thesaid contacts being respectively disposed in said" grooves and rigidly held'between the arcuate p1ates:and the separator plate with the terminal portions of the contacts disposed inthe grooves of one plate.

extending at an angle with respect to the terminal portion of the contacts in'the grooves-in the other plate and the inner surface of each contact contacting thebase of each groove and filling the same--and'the outer surface of each.

contact being-flush-with the adjacent face portionof each plate-between the respective groovestherein and each-outerface ofeach contactbeing against the adjacent portionofithe separator plate.

5: A selector contact bank as-defined inand; by claim 4, and a screening member'interposed.

between each ofsaidlevels.

HUBER/I" 'HARVEYJ REFERENCES CITED The following references are of recordin' the fileof this patent:

UNITED STATES PATENTS Number Name Date 1,139,764 Hodgson May.18;1915 1,283,563 Roberts; ,Nov. 5, 1918 1,819,675 Chaplin "Aug. 18, 1931, 1,971,481 Erickson Aug,28-, 1934 2,057,865; Wagner Oct. 20, 1936.

FOREIGN 'P-ATENTS Number Country Date 596,820 Germany Ma 11, 1934 

